Flashcards in Absorption, attenuation, and grids Deck (23)
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1
PEA results in complete
x-ray absorption
2
compton causes
scatter
3
attenuation
some penetrating x-rays are absorbed by tissues
4
exponential attentuation
absorption depends on tissues thickness
5
HVL measures x-ray
quality/penetrability
6
HVL
thickness of absorbing material needed to reduce x-ray intensity by half
7
types of filtering
1. tungsten anode
2. x-ray tube housing
3. added filtration
8
exposing body parts with unequal thickness
compensatory filter
9
primary bean attenuated by 90%
tenth value layer (TVL)
10
scatter intensity depends on..
kVp, beam field size, and patients thickness
11
grid is a series of
lead strips --> cleans up scatter (up to 80%)
12
grid ratio
R=h/D
13
most frequent grid ratio used
8:1 to 10:1
14
higher ratio grids
less scatter but more radiation exposure is needed
15
paralleled grid flaw
grid cut-of artefact
16
grid cut-off
undesirable absorption of primary x-rays
17
grid cut-off is inversely related to
source image distance (SID)
18
disadvantages of moving grids
bulky mechanism and blurring effect
19
stationary grids mostly used for
portable radio and upright horizontal views
20
higher grid ratio can be met by
increase in mAs
21
mAs should be increased
10% for each cm of air-gap
22
commonly obtained using air-gap technique
lateral cervical
23
